Problem: $ { {2} \times \left[\begin{array}{rr}{3} & {-1} \\ {1} & {-1}\end{array}\right] = {?} } $
To multiply a matrix by a number, multiply each item of the matrix by the number. ${\left[\begin{array}{rr}{2}\times{3} & {2}\times{-1} \\ {2}\times{1} & {2}\times{-1}\end{array}\right]}$ Now, simplify: ${\left[\begin{array}{rr}{6} & {-2} \\ {2} & {-2}\end{array}\right]}$